This application is a 35 USC 371 application of PCT/DE 99/00862 filed on Mar. 24, 1999.
The invention relates to a radial piston pump for generating high fuel pressure in fuel injection systems of internal combustion engines, in particular in a common rail injection system, having a drive shaft which is supported in a pump housing and is embodied eccentrically or has camlike protuberances in the circumferential direction, and having preferably a plurality of pistons, disposed radially in a respective element bore relative to the drive shaft, which are movable back and forth in the radial direction by rotation of the drive shaft in the applicable element bore, and one plate is retained on each of the ends toward the drive shaft of the pistons.
One such radial piston pump is known for instance from German Patent Disclosure DE 42 16 877. In the known radial piston pump, the plate is retained on the associated piston by a clamp device in the form of a plate disk with inward-recurved clamp arms that engage the plate around its edge. When the clamp devices are in storage, it repeatedly happens that the inward-recurved clamp arms of different clamp devices catch on one another. Separating the individual clamp devices again takes time and slows down the assembly of the radial piston pump.
The object of the invention is therefore to furnish a radial piston pump that can be assembled simply and quickly. In particular, the individual clamp devices are to be prevented from catching on one another during storage.
In a radial piston pump for generating high fuel pressure in fuel injection systems of internal combustion engines, in particular in a common rail injection system, having a drive shaft which is supported in a pump housing and is embodied eccentrically or has camlike protuberances in the circumferential direction, and having preferably a plurality of pistons, disposed radially in a respective element bore relative to the drive shaft, which are movable back and forth in the radial direction by rotation of the drive shaft in the applicable element bore, and one plate is retained on each of the ends toward the drive shaft of the pistons, this object is attained in that in the surface facing toward the piston of the plate, one or more recesses are disposed, which are engaged in the assembled state by snap hooks that are embodied on a plate retainer which is mounted on the associated piston. Besides simple, fast assembly, the snap hooks offer the advantage that they do not warp as much upon assembly as the clamp arms known from the prior art. This reduces the load on the material during assembly and leads to a longer service life of the radial piston pump.
In a first variant of the invention, the aforementioned object is attained in that in the surface of the plate facing toward the piston, a blind bore with a circumferential groove is recessed out of the middle, which groove is engaged by a snap ring that is retained in a notch on the piston. This variant offers the advantage not only of faster assembly but also that it makes do with fewer parts than the known version. This reduces the production costs of the radial piston pump.
In a second variant of the invention, the aforementioned object is attained in that in the surface of the plate facing toward the piston, a blind bore and two parallel bores are recessed out in the middle, which parallel bores extend transversely to the blind bore in such a way that the center lines of the bores are tangent to the jacket face of blind bore, and the bores serve to receive two pins, which in the inserted state engage a notch that is made on the piston. With this second variant, the same advantages as with the first variant are attained.
A special feature of the second variant of the invention is characterized in that the two pins are joined by a crosspiece to form a clamp. This feature has the advantage that the pins are automatically fixed axially when the crosspiece comes to a stop against the plate.
A further feature of the second variant of the invention is characterized in that the crosspiece, in the inserted state of the clamp, is secured by a protrusion that is formed on the plate. As a result, it is advantageously assured that the pins during operation will not slip out of the bores.
Further advantages, characteristics and details of the invention will become apparent from the ensuing description, in which several exemplary embodiments of the invention are described in detail in conjunction with the drawings. The characteristics recited in the claims and in the description can each be essential to the invention individually or in arbitrary combination.